Liquid toning apparatus

ABSTRACT

Liquid toning apparatus is disclosed for developing a latent electrostatic image on the surface of a dielectrically coated sheet of flexible paper. The apparatus comprises a reservoir adapted to contain liquid toner at a predetermined liquid toner surface level. A rotatable cylinder is mounted for rotation about a cylinder axis disposed above and substantially parallel the liquid toner surface level a distance less than the radius of the cylinder whereby a portion of the rotatable cylinder is positioned above the liquid toner surface level, and another portion of the rotatable cylinder is simultaneously positioned beneath the liquid toner surface level. A plurality of juxtapositioned rollers are mounted adjacent the rotatable cylinder for rotation about a plurality of roller axes disposed above and substantially parallel the cylinder axis with the rollers and the rotatable cylinder defining therebetween an arcuate toning station. Guide means are also provided for guiding sheets of flexible paper into the arcuate toning station.

United States Patent 1191 Dahlquist et al. Mar. 27, 1973 LIQUID TUNING APPARATUS Primary Examiner.lohn P. McIntosh 75 Inventors: John A. Dahlquist; Ivor Brodie, both & Hamnck of Palo Alto, Calif. [57] CT [73] Assignee: Photophysits, Inc., Mountain View,

Califi L1qu1d toning apparatus is disclosed for developlng a latent electrostatic image on the surface of a dielectri- [22] Flled: 1971 cally coated sheet of flexible paper. The apparatus 2 App] 130 904 comprises a reservoir adapted to contain liquid toner at a predetermined liquid toner surface level. A rotatable cylinder is mounted for rotation about a l 5 "118/ 1 18/249 3435; cylinder axis disposed above and substantially parallel o I 6 t 1 the toner Surface level a less than the [58] Field of Search ..118/246, DIG. 23, 258, 259, radius of the cylinder whereby a portion of the rotatw ll8/DIG 2 249 ble cylinder is positioned above the liquid toner surface level, and another portion of the rotatable [56] References Cited cylinder is simultaneously positioned beneath the UNITED STATES PATENTS liquid toner surface level, A plurality of juxtaposi- 2 7 6 V 3 l 4 H8 246 tioned rollers are mounted adjacent the rotatable ,3 0, 17 9 5 Campf cylinder for rotation about a plurality of roller axes 3,083,684 4/1963 Carlson... 118/246 b0 b n n l h 771,662 10 1904 Peck 118/246 P F e and e Para t 6 cy 1,399,160 12 1921 Sevigne ...118/259 x aXlS Wlth the mllers and the rotatable Cylmder definmg 2,289,798 7 1942 Nadeau e131. .,11s 25s therebetween an arcuate toning station. Guide means 3,492,840 970 Korsche 118/258 X are also provided for guiding sheets of flexible paper 7/1949 lle into the arcuate toning station. ,2 ement PATENTEUHARZYIBYS SHEET 10F 2 INVENTORS JOHN A. DAHLQUIST BY IVOR BRODIE ATTORNEYS PATENTEBHARZ'HBYES 3 5 7 sum em 2 INVENTORS JOHN A. DAHILQUISTV BY IVOR BRODIE ATTORNEYS mourn TOWING AwAnArus BACKGROUND OF THE INVENTION This invention relates generally to means for developing latent electrostatic images, and particularly to means for applying liquid toner to the surface of a dielectrically coated sheet of flexible paper having a latent electrostatic image thereon.

With certain electrostatic copy processes, such as those in which the copy paper is charged in the presence of a corona prior to optical imaging, a relatively high charge density such as that which produces 400 to 600 volts of potential is typically present on the paper surface. When such images are developed with liquid toner the paper need be coated with the toner for only a very short period of time in developing the image. With other electrostatic copy processes, however, such as those utilizing transfer electrophotography techniques as described in R.W. Shafferts text entitled Electrophotography (Focal Press), a relatively low charge density is present such as that which produces in the order of 50 volts on the surface of the record copy. When subsequently developed with liquid toner, a copy sheet having this relatively low electrostatic charge density on the surface thereof mustbe in contact with the liquid toner for a greater period of time to achieve sufficient development. This, of course, arises from the fact that here is less attractive force between the charge pattern on the paper surface and the oppositely charged toner particles.

Heretofore, electrostatic images of relatively low of liquid toner for a brief but significant period of time.-

A principal problem with this procedure has been that both sides of the record copy are wetted and absorb toner fluid. The toning of both sides is, of course, unnecessary and results is a high consumption of toner. This problem can be overcome by coating the back side of the paper with a sealer but such, of course, produces added costs and an unnatural feel to the paper.

Accordingly, it is a general, object of the present invention to provide improved liquid toning apparatus.

More specifically, it is a principal object of the present invention to provide improved means for ap plying liquid toner to the surface of a dielectrically coated sheet of flexible paper having a latent electrostatic image thereon for a brief but predetermined and controlled period of time while not applying toner to the reverse side surface of the sheet.

SUMMARY OF THE INVENTION Briefly described, the present invention is liquid toning apparatus for developing a latent electrostatic image on the surface of a dielectrically coated sheet of flexible paper. The apparatus comprises a reservoir adapted to contain liquid toner at a predetermined liquid toner surface level, and a rotatable cylinder mounted for rotation about a cylinder axis disposed above the liquid toner surface level a distance less than the radius of the cylinder whereby one portion of the rotatable cylinder is positioned above the liquid toner surface level and another portion thereof is positioned beneath the liquid toner surface level. Means are also provided for rotating the rotatable cylinder whereby successive portions of the cylinder may be positioned beneath the liquid toner surface level. A plurality of juxtapositioncd rollers are mounted adjacent the rotatable cylinder for respective rotation about a plurality of roller axes disposed above and substantially parallel the cylinder axis with the plurality of rollers and the rotatable cylinder defining therebetween an arcuate toning station. Guide means are provided for guiding sheets of flexible paper into the arcuate toning station.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a diagrammatic view in perspective ofliquid toning apparatus incorporating principles of the present invention.

FIG. 2 is a giagrammatical side view of the apparatus shown in FIG. 1 with one wheel removed for clarity.

FIG. 3 is a diagrammatical front view of the apparatus shown in FIGS. 1 and 2.

FIG. 4 is a fragmentary view in elevation of a guide member of the apparatus shown in the other figures.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now in more detail to the drawing there is shown liquid toning apparatus incorporating principles of the present invention and comprising a reservoir 10 adapted to be filled to surface level 12 with liquid toner. A suitable automatic toner replenishment system R, such as that actuated by the rising and lowering of a float, is provided. A toner cylinder 14, which is driven by motor M, is mounted for rotation about axle 16 adjacent the top of reservoir 10. Two wheels 18 are also mounted to axle 16 in spaced relation with the ends of toner cylinder 14 with two upper portions 19 of the sides of reservoir 10 positioned therebetween.

Above wheels 18 and toner cylinder 14 are mounted five rollers 20 as shown in FIG. 2. For clarity only three of these rollers are shown in FIG. 1 and only one is shown in FIG. 3. Each roller is mounted in a vertical guide slot 22 as shown in FIG. 4, which structure permits restricted vertical movement of the rollers above the positions they each occupy in FIGS. l-3.

As most clearly shown in FIG. 3, the diameter of the central portion 20 of each roller 20 is less than the diameter of the two end portions 20" thereof. End portions 20" are located above wheels 18 while central portions 20' are located above toner cylinder 14. As wheels 18 have the same diameter as toner cylinder 14 and are coaxially mounted thereto the central portion 20' of the rollers is always spaced from the toner cylinder, whereas end portions 20" may rotatably rest on wheels 18. When each roller rests on wheels 18, the axes thereof then lie along an arc of a circle having its center located approximately on the axis of toner cylinder 14 and wheels 18. If desired, rollers 20 may alternatively have uniform diameter and wheels 18 a diameter greater than that of cylinder 14 and still accomplish the purpose yet to be described. I

An elongated arcuate vessel 30 is mounted within reservoir 10 above surface level 12. An impeller pump P is located beneath surface level 12 and vessel'30. A tube 32 is' connected to the outlet of pump P and to an intake aperture in vessel 30. A small drain 34 is provided in the bottom of the vessel. A metallic plate 36 is mounted to the top of vessel 30 which plate has a re-entrant portion disposed beneath the top of the vessel and a cylindrical portion disposed thereabove adjacent toner cylinder 14. The cylindrical portion of plate 36 is disposed coaxially the toner cylinder and in spaced relation therewith. The distance between plate 36 and toner cylinder 14 is quite small, such as 20-30 mils, and forms a capillary for liquid toner. The vehicle of the toner preferred by Applicant is Isopar G sold by the Humble Oil Corporation. In use with toners having higher surface tension, the spacing between plate 36 and toner cylinder 14 could, of course, be greater and still function as a capillary.

Above reservoir is mounted a guide scoop 38 having a scoop lip 39 disposed adjacent toner cylinder 14 between a roller and the top edge of plate 36. Another guide scoop 41 is likewise mounted above reservoir 10 with scoop lip 42 disposed adjacent the toner cylinder and another roller.

In operation, pump P pumps liquid toner within reservoir 10 upwardly through tube 32 and into vessel 30 at a flow rate much greater than drain 34 can accommodate. Vessel 30 thus completely fills with toner and overflows as shown by arrow 47. Toner cylinder 14 is then rotated by motor M whereby successive portions thereof are driven beneath toner surface level 40 within vessel 30. This action causes the entire surface of the toner cylinder to become coated with a film 50 of liquid toner. The cylindrical capillary formed by cylinder 14 and plate 36 causes an additional input of toner along the surface of the revolving toner cylinder above surface level 40 which input terminates just beneath lip 39 of guide scoop 38. This combined action insures the presence of a film of toner on the toner cylinder at the point flexible paper departs scoop lip 39 and passes beneath the first of rollers 20 into contact with toner film 25. Paper 25 is then carried by rotating toner cylinder 14 successively beneath the other rollers 20 which may lift slightly against the force of gravity within guide slots 22 to accommodate space occupied by the paper therebeneath. Finally, paper 25 exits the last of rollers 20 and is directed away from the toner cylinder by guide scoop 41 as indicated by arrow 46. When the toning operation is completed, the action of motor M and pump P is arrested. The rotation of toner cylinder 14 will likewise be terminated and the toner fluid slowly drained from vessel 30 through drain 34.

Toning of flexible sheets of paper having latent electrostatic images thereon by use of the just described apparatus results in a number of advantages over that offered by the devices of the prior art. First, the paper is coated with liquid toner fluid for a significant period of time which may be of critical importance for proper development where the electrostatic image patterns are of relatively low charge density. Also, only one side of the paper is so coated which in turn negates any necessity of coating the other side with a sealer. In addition, the film of applied toner is quite evenly applied due to the combined action of revolving the toner fluid and of applying additional toner thereto by capillary action just prior to contact by the paper. It should also be noted that axle 16 is disposed above the toner and thus need not be sealed to prevent toner leakage. Also, neither wheels 18 nor rollers 20 are wetted by the fluid. And, when not in use, toner fluid is automatically removed from contact with the toner cylinder which action helps prevent formation of dried or slurry residual toner thereon.

It should be understood that the just described embodiment is merely illustrative of principles of the invention and that many modifications may be made thereto without departing from the spirit and scope of the invention as set forth in the following claims.

What is claimed is:

1. Liquid toning apparatus for developing a latent electrostatic image on the surface of a dielectrically coated sheet of flexible paper comprising:

a reservoir adapted to contain liquid toner at a predetermined liquid toner surface level;

a rotatable cylinder having a central section and two end sections and mounted for rotation about a cylinder axis disposed above and substantially parallel to said liquid toner surface level, said cylinder axis being disposed above said liquid toner surface level a distance less than the cylinder radius of said central section whereby a portion of the central section of said rotatable cylinder is positioned above said liquid toner surface level and another portion of the central section of said rotatable cylinder is simultaneously positioned beneath said liquid toner surface level, said two end sections being removed from said liquid toner surface;

means for rotating said rotatable cylinder whereby successive portions of said central section of said cylinder may be positioned beneath said liquid toner surface level; plurality of juxtapositioned rollers mounted adjacent each of said end sections of said rotatable cylinder for respective rotation about a plurality of roller axes disposed above and substantially parallel said cylinder axis, said rollers engaging said end sections along an are over the top of said end sections and serving to drivably engage the edges of the paper between the cylinder end sections and the associated plurality of rollers;

means extending over the central section of said rotatable cylinder and spaced therefrom and defining therebetween an arcuate toning station; and

guide means for guiding sheets of flexible paper into said arcuate toning station with the edges of the sheet between said rollers and said cylinder end sections.

2. Liquid toning apparatus in accordance with claim 1 wherein each of said roller axes is positioned substantially equidistantly from said cylinder axis.

3. Liquid toning apparatus in accordance with claim I wherein said means extending over the central section of said rotatable cylinder comprising a central section in each of the rollers engaging each of the end sections of said rotatable cylinder, each of said central sections of said rollers being spaced from said-cylinder central section.

4. Liquid toning apparatus in accordance with claim 1 wherein one of said end sections of said cylinder comprises a first wheel coaxially mounted to said rotatable cylinder in spaced relation with one end of said rotatable cylinder, and wherein the other of said end sections of said cylinder comprises a second wheel coaxially mounted to said rotatable cylinder in spaced relation with the other end of said rotatable cylinder.

5. Liquid toning apparatus in accordance with claim 4 wherein said rollers are mounted in contact with said first and second wheels whereby rotation of said wheels by said rotating means imparts rotation to said rollers.

6. Liquid toning apparatus in accordance with claim 1 wherein said guide means comprises an arcuate scoop having a lip disposed adjacent said rotatable cylinder and said means extending over the central section of said rotatable cylinder at the entrance end of said toning station.

7. Liquid toning apparatus in accordance with claim 6 comprising a second arcuate scoophaving a lip disposed adjacent said rotatable cylinder and said means extending over the central section of said rotatable cylinder at the exit end of said toning station.

8. Liquid toning apparatus in accordance with claim 1 having a vessel mounted within said reservoir in spaced relation with the central section of said rotatable cylinder.

9. Liquid toning apparatus in accordance with claim 8 wherein said vessel is cylindrical and is mounted coaxially with said rotatable cylinder.

10. Liquid toning apparatus in accordance with claim 9 comprising pump means for pumping liquid toner disposed in said reservoir beneath said vessel up and into said vessel, and drain means for draining liquid toner from said vessel into portions of said reservoir disposed beneath said vessel.

11. Liquid toning apparatus in accordance with claim 8 comprising capillary means having a portion thereof disposed between the central section of said rotatable cylinder and said vessel.

12. Liquid toning apparatus in accordance with claim 11 wherein said portion of said capillary means is disposed beneath said predetermined liquid toner sur face level and wherein said capillary means has a second portion thereof disposed above said predetermined liquid toner surface level.

13. Liquid toning apparatus in accordance with claim 12 wherein said second portion of said capillary means is disposed between the central section of said rotatable cylinder and said guide means whereby liquid toner in said vessel may be drawn upwardly into contact with said rotatable cylinder at a point adjacent said guide means and said toning station. 

1. Liquid toning apparatus for developing a latent electrostatic image on the surface of a dielectrically coated sheet of flexible paper comprising: a reservoir adapted to contain liquid toner at a predetermined liquid toner surface level; a rotatable cylinder having a central section and two end sections and mounted for rotation about a cylinder axis disposed above and substantially parallel to said liquid toner surface level, said cylinder axis being disposed above said liquid toner surface level a distance less than the cylinder radius of said central section whereby a portion of the central section of said rotatable cylinder is positioned above said liquid toner surface level and another portion of the central section of said rotatable cylinder is simultaneously positioned beneath said liquid toner surface level, said two end sections being removed from said liquid toner surface; means for rotating said rotatable cylinder whereby successive portions of said central section of said cylinder may be positioned beneath said liquid toner surface level; a plurality of juxtapositioned rollers mounted adjacent each of said end sections of said rotatable cylinder for respective rotation about a plurality of roller axes disposed above and substantially parallel said cylinder axis, said rollers engaging said end sections along an arc over the top of said end sections and serving to drivably engage the edges of the paper between the cylinder end sections and the associated plurality of rollers; means extending over the central section of said rotatable cylinder and spaced therefrom and defining therebetween an arcuate toning station; and guide means for guiding sheets of flexible paper into said arcuate toning station with the edges of the sheet between said rollers and said cylinder end sections.
 2. Liquid toning apparatus in accordance with claim 1 wherein each of said roller axes is positioned substantially equidistantly from said cylinder axis.
 3. Liquid toning apparatus in accordance with claim 1 wherein said means extending over the central section of said rotatable cylinder comprising a central section in each of the rollers engaging each of the end sections of said rotatable cylinder, each of said central sections of said rollers being spaced from said cylinder central section.
 4. Liquid toning apparatus in accordance with claim 1 wherein one of said end sections of said cylinder comprises a first wheel coaxially mounted to said rotatable cylinder in spaced relation with one end of said rotatable cylinder, and wherein the other of said end sections of said cylinder comprises a second wheel coaxially mounted to said rotatable cylinder in spaced relation with the other end of said rotatable cylinder.
 5. Liquid toning apparatus in accordance with claim 4 wherein said rollers are mounted in contact with said first and second wheels whereby rotation of said wheels by said rotating means imparts rotation to said rollers.
 6. Liquid toning apparatus in accordance with claim 1 wherein said guide means comprises an arcuate scoop having a lip disposed adjacent said rotatable cylinder and said means extending over the central section of said rotatable cylinder at the entrance end of said toning station.
 7. Liquid toning apparatus in accordance with claim 6 comprising a second arcuate scoop having a lip disposed adjacent said rotatable cylinder and said means extending over the central section of said rotatable cylinder at the exit end of said toning station.
 8. Liquid toning apparatus in accordance with claim 1 having a vessel mounted within said reservoir in spaced relation with the central section of said rotatable cylinder.
 9. Liquid toning apparatus in accordance with claim 8 wherein said vessel is cylindrical and is mOunted coaxially with said rotatable cylinder.
 10. Liquid toning apparatus in accordance with claim 9 comprising pump means for pumping liquid toner disposed in said reservoir beneath said vessel up and into said vessel, and drain means for draining liquid toner from said vessel into portions of said reservoir disposed beneath said vessel.
 11. Liquid toning apparatus in accordance with claim 8 comprising capillary means having a portion thereof disposed between the central section of said rotatable cylinder and said vessel.
 12. Liquid toning apparatus in accordance with claim 11 wherein said portion of said capillary means is disposed beneath said predetermined liquid toner surface level and wherein said capillary means has a second portion thereof disposed above said predetermined liquid toner surface level.
 13. Liquid toning apparatus in accordance with claim 12 wherein said second portion of said capillary means is disposed between the central section of said rotatable cylinder and said guide means whereby liquid toner in said vessel may be drawn upwardly into contact with said rotatable cylinder at a point adjacent said guide means and said toning station. 